1. Field of Invention
The present invention relates generally to specially designed magnesium-aluminum (“Mg—Al”) alloys and medical uses thereof in a hemodynamic environment, and, more particularly to devices for sealing an opening formed through biological tissue (such as blood vessels) made from such specially designed magnesium-aluminum alloys.
2. Description of the Related Art
Certain Mg alloys are known and have been used to form devices for sealing an opening formed through biological tissue (such as blood vessels). See, e.g., U.S. Pat. Pub. No. 20110046665, paras. [0015], [0018], [0025], and [0038] (describing a closure device for sealing an opening formed through biological tissue which comprises a footplate, a plug, and a wire, and where the footplate, wire, and/or plug portion is made from a biocompatible and biocorrodible metal comprising certain magnesium alloys).
Aluminum additions to Mg have a significant effect on corrosion rate, though a variety of trends can be found. Pardo reports that a 3% Al addition in Mg alloy AZ31 slightly decreases corrosion rate in 3.5% NaCl solution and that Al addition s of 8 to 9 wt. % found in AM80 and AZ91 strongly reduce corrosion rate in electrochemical testing in 3.5% NaCl solution (See A. Pardo, M. C. Merino, A. E. Coy, F. Viejo, R. Arrabal, S. Feliu, Jr., Electrochim. Acta, 53, 7890-7902 (2008)). Abady and co-workers found in electrochemical studies of alloys from 0 to 15 wt. % Mg exposed to chloride-free buffer solutions that corrosion rate peaked at 5 wt. % Al and decreased significantly in alloys with 10 and 15% Al (See G. M. Abady, N. H. Hilal, M. El-Rabiee, W. A. Badawy, Electrochim. Acta, 55, 6651-6658 (2010)). Kita et al. found from electrochemical testing that corrosion rate increases in dilute chloride environments with increasing Al content over the range of 1 to 9 mass percent (See H. Kita, M. Kimoto, T Kudo, J. Japan Inst. Of Metals, 69, 805-809 (2005)).
In simulated biological environments, the corrosion rate dependence appears to indicate that increasing Al content decreases rate. From electrochemical corrosion rate determinations of Mg-xAl-3Zn alloys exposed to quiescent modified simulated body fluid (SBF) at 36.5° C., corrosion rates were found to decrease strongly with increasing Al content (See Z. Wen, C. Wu, C. Dai, F. Yang, J. Alloys and Compounds, 488, 392-399 (2009)). Kirkland reported corrosion rates in Minimal Essential Medium (MEM) at 37° C. showing strongly decreased corrosion rate with increasing Al concentration over the range of 0 to 9 weight percent (See N. T. Kirkland, J. Lespagnol, N. Birbilis, M. P. Staiger, Corrosion Sci., 52, 287-291 (2010)).
Description of the Related Art Section Disclaimer: To the extent that specific patents/publications are discussed above in this Description of the Related Art Section or elsewhere in this Application, these discussions should not be taken as an admission that the discussed patents/publications are prior art for patent law purposes. For example, some or all of the discussed patents/publications may not be sufficiently early in time, may not reflect subject matter developed early enough in time and/or may not be sufficiently enabling so as to amount to prior art for patent law purposes. To the extent that specific patents/publications are discussed above in this Description of the Related Art Section and/or throughout the application, they are all hereby incorporated by reference into this document in their respective entirety(ies).